extern int printf(const char* format, ...);
static void kb_wait_1(void) {
    unsigned long timeout = 2;
    do {
        if (1)
            printf("timeout=%ld\n", timeout);
        else {
            while (1)
                printf("error\n");
        }
        timeout--;
    } while (timeout);
}
static void kb_wait_2(void) {
    unsigned long timeout = 2;
    do {
        if (1)
            printf("timeout=%ld\n", timeout);
        else {
            for (;;)
                printf("error\n");
        }
        timeout--;
    } while (timeout);
}
static void kb_wait_2_1(void) {
    unsigned long timeout = 2;
    do {
        if (1)
            printf("timeout=%ld\n", timeout);
        else {
            do {
                printf("error\n");
            } while (1);
        }
        timeout--;
    } while (timeout);
}
static void kb_wait_2_2(void) {
    unsigned long timeout = 2;
    do {
        if (1)
            printf("timeout=%ld\n", timeout);
        else {
        label:
            printf("error\n");
            goto label;
        }
        timeout--;
    } while (timeout);
}
static void kb_wait_3(void) {
    unsigned long timeout = 2;
    do {
        if (1)
            printf("timeout=%ld\n", timeout);
        else {
            int i = 1;
            goto label;
            i = i + 2;
        label:
            i = i + 3;
        }
        timeout--;
    } while (timeout);
}
static void kb_wait_4(void) {
    unsigned long timeout = 2;
    do {
        if (1)
            printf("timeout=%ld\n", timeout);
        else {
            switch (timeout) {
            case 2:
                printf("timeout is 2");
                break;
            case 1:
                printf("timeout is 1");
                break;
            default:
                printf("timeout is 0?");
                break;
            };
            /* return; */
        }
        timeout--;
    } while (timeout);
}
int main() {
    printf("begin\n");
    kb_wait_1();
    kb_wait_2();
    kb_wait_2_1();
    kb_wait_2_2();
    kb_wait_3();
    kb_wait_4();
    printf("end\n");
    return 0;
}
